I have the C910 and like it. I don't use it much. Just the occassional photo and Skype once a month or so.
You don't say what you'll be using the webcam for. That might make a difference on recommendations.
I'm looking at security apps right now. Motion detection and such. Also for fun apps for the kids to play with.
No matter how good the camera your Skype or other vidoe chats will only be as good as the connections on BOTH ends of the call.